Iran’s Deputy Foreign Minister Abbas Araqchi says an initial nuclear deal is likely to be reached on Iran’s nuclear program after a planned meeting between Iranian Foreign Minister Mohammad Javad Zarif and US Secretary of State John Kerry in Geneva.

"I'm a bit optimistic," Araqchi told reporters after the first day of talks between Iran and the five permanent U.N. Security Council members and Germany.

The hoped-for agreement -- seen as a first step ahead of further talks on a final deal -- could see Tehran to decide about changes on the dimension of its nuclear activities for as long as six months in exchange for some relief from the Western sanctions.

However the administration of US President Barack Obama says it is “premature” to criticize a deal being discussed in Geneva over Iran’s nuclear energy program.

"There is not an agreement at this point," John Kerry told reporters shortly after arriving in Geneva Friday to help seal what is hoped to be a landmark deal with Tehran.

Kerry, who broke off a Middle East tour to join the ongoing negotiations in the Swiss city, stressed that "there are still some very important issues on the table that are unresolved."

In addition to Kerry, the foreign ministers of France, Britain and Germany also arrived Friday following last-minute announcements they would join the talks.

Iranian Foreign Minister Mohammad Javad Zarif also cancelled a trip to Rome to continue the talks.

Iran nuclear talks may be continued for third day too.

The unexpected convening of some of the world's most high-ranking diplomats has sparked widespread hopes that a deal may be in sight.

In other developments, Director General of the International Atomic Energy Agency (IAEA) Yukia Amano will travel to Tehran next week for talks on inspections of Iran’s nuclear sites.